Ok, I tried to talk you out of it, but here goes! You might try these suggestions, but in the end the best system is the one that works for you! Start with what you know about yourself when you evaluate someone's organizational ideas. If your stomach clenches just thinking about doing something, that isn't the idea for you.
The main thing is to have an easily accessible assigned place for everything that needs to get organized. The "easily accessible" part is important. Stuff you don't have to deal with all the time can go in the garage or the basement (ex: a bin for items to go to the Goodwill). Stuff you need to get your hands on easily (ex: kid's school papers) should probably be in the kitchen. And remember, empty space is as important as storage space for stuff you need to use. Stuff you never need can be crammed into a small place in the basement. Office supplies should be placed somewhere where they can be easily grabbed, not crammed in so tightly you have to move 5 things to get to the paperclips you need.
1. Craft projects, party ideas, school plans.
Rip these ideas out of the magazines, newspapers, etc as soon as you finish reading them, then throw the magazine out! Piles of magazines you're going to go through "eventually" depress anyone. Set up a file cabinet with individual hanging files for craft projects, party ideas, school plans, etc. If you can stand to file this stuff right away, do it. Otherwise get a big box that you can hide somewhere convenient and throw all these ideas in there to file when you get around to it. You'll feel more organized when you chuck those things into your IDEA box than you do with them spread all over your floor and tables, and although you may have to look through the box to find what you want until you file the stuff, at least you'll have only one place to look.
2. Incoming mail, coupons, special offers
I've set up my bills so they can all be paid once a month. When I bring mail into the house I sort it immediately. Bills get thrown into a bottom kitchen drawer that only holds my bill-paying stuff, and then everything is there when the end of the month comes.
Special offers (like really good 20% off coupons at Bed, Bath and Beyond,etc) get put in a neat pile on one side of my kitchen desk, because I am likely to forget to bring them to the store if they aren't in plain sight. When the pile gets high, I sort through it to throw out all the expired offers, but that can be done when the mood hits me every few months.
Coupons are another story. I had a great organizer for coupons to take to the store, but even I didn't enjoy all the work involved in keeping up with the coupons. So you really have to decide if saving cents off at the grocery store is worth it to you. If you decide it is, you might want to make a deal with yourself to find the cheapest supermarket in your area and shop there for your weekly list. You can then mentally trade driving a few minutes more once a week for the chance not to have to wrangle coupons, and alleviate your guilt that way.
3. Kids school stuff. I like Disneygal's idea. I'm all for plastic drawers in the kitchen. Ideally you'll sort through the papers before they get put into the drawer in the first place. Ideally-ideally, you'll ruthlessly sort again before putting all the can't-live without-them sentimental papers in the child's bin in the basement. I would buy plastic drawers that aren't gigantic, so that they would get full fast, and would almost have to get sorted in small doses. Once during the summer, go through each child's bin and, if you haven't already been ruthless, toss most of the stuff (which, believe me, will by then seem worthless). We keep "memory trunks" stacked in our basement of sentimental stuff we've collected through the years. The "keep" stuff from the child's basement bin can be put there.
(I also keep a small upright bag on my kitchen desk for sentimental stuff that gets accumulated. Things like used Disney tickets get thrown in there right after the trip. When this bag is full, I throw the whole thing into the current memory trunk, and start a new bag. This gives me a place to put those small items that I want to save that would ordinarily sit on my dresser waiting for ???)
As far as the return to school stuff goes, that's why God made refrigerator magnets. Post this stuff where you have to see it. Ideally you will fill in the forms as soon as the child comes in the door, but I don't know anyone with that kind of life. Just post it on the refrigerator door to remind you to sign it before it is due.
Hope these ideas, and the ones others are contributing, help, but just don't be too hard on yourself. Nothing's worth that!
